#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<stdio.h>
#include<cmath>
using namespace std;
int main()
{
	float s;
	float sum = 0;
	int n = 0;
	scanf("%f", &s);
	if (1 <= s && s <= 100)
	{
		while (sum <= s)
		{
			sum += 2 * pow(0.98, n);
			n++;
		}

	}
	cout << n << endl;
	return 0;
}